1. Field of the Invention
This invention relates to fiber reinforced polymer (FRP), and more specifically, to lightweight FRP composite decks for structural support systems or FRP walls for soil or other retaining systems, and to methods for manufacturing and installing lightweight FRP composite decks or walls.
2. Related Art
Structural panels are continually needed in constructing and repairing walls, floors, decking, bridges, roofs, and the like. In the prior art, conventional construction materials, e.g., steel, concrete, and wood, are used for high performance deck and wall structures because such materials typically have a high load bearing capacity.
There are several disadvantages associated with using such conventional construction materials in structural panels. First, such structural panels have a short service life in that they degrade over time: steel panels corrode, concrete panels spall such that they require repair or replacement every ten to fourteen years, and wood panels rot. Second, such structural panels tend to be very heavy in order to achieve the required load bearing capacity for the specific application. Third, such structural panels require a long time for creation and erection because they are typically built and installed on site.
To accommodate some of the disadvantages with conventional construction materials, the prior art includes fiber reinforced polymer (FRP) composite materials made with a honeycomb core and an outer skin which absorb water with time. In addition, panels made of conventional FRP composite materials have lineal profiles mainly reinforced with continuous fibers in the axial or long direction.
There are several disadvantages associated with using such conventional FRP materials in structural panels. First, although conventional FRP composite materials are lightweight, they lack the required load-bearing capacity to handle high performance deck and wall structures. Therefore, conventional FRP composite materials are used only for light duty floor systems and building panels. Second, conventional FRP composite panels without fiber continuity between the core and outer skin often develop moisture ingress and resin-dominated failure with respect to the honeycomb core and outer skin. Third, the lineal profile and primary use of continuous fibers in the axial direction result in a reduced load bearing capacity.
Therefore, there is a need for a FRP composite panel that is lightweight, yet has a high load rating due to high strength to weight ratio. There is a further need for a FRP composite panel that has a long service life due to its resistance to corrosion There is still a further need for a FRP composite panel that is easy and quick to erect and become operational.
There is also a need for a FRP composite deck or wall system that is lightweight, yet can withstand the heavy loads associated with highway, retaining walls, bridges, bridge abutments, and decking systems. The FRP composite deck or wall systems must also have a long service life and be prefabricated to allow for easy and quick installation.
One panel and deck system addressing these needs is the FRP panel disclosed in U.S. Pat. No. 6,309,732. Although this ""732 panel resolves many of the disadvantages with the other conventional panel and deck systems, there is still a need to further improve the FRP panel. In one embodiment, the ""732 panel system comprises two separate locking pieces: a double trapezoid component and a hexagon component, wherein the hexagon component is used to interlock two adjacent double trapezoid components. This interlocking and assembly of a deck system using the ""732 components is very straightforward; however, there is still a need to improve the time and effort required for assembly of a deck or panel.
The lightweight FRP composite modular panel (xe2x80x9cModular Panelxe2x80x9d) of the present invention solves the problems and disadvantages of conventional structural panels by providing a FRP composite module that interlocks with other similarly designed modules. Specifically, each FRP module has a female, receiver, end and a male, inserter, end such that the inserter of a first FRP module interlocks with, or xe2x80x9csnapsxe2x80x9d or xe2x80x9cslidesxe2x80x9d into, a receiver of an adjacent second FRP module. Once interlocked, the two connected FRP modules are further secured by either adhesive, mechanical and/or thermal connections.
The FRP modules are snapped together and used for infrastructure and constructed facilities such as heavy duty interstate bridge decks, lightweight bridge deck for secondary roadway bridge structures, floating off-shore platforms, ship decks, bridge decks, wall/floor/roof panels, sound barriers, and trench support reinforcements. Optionally, an application of FRP modules may further comprise filling the interior spaces of the FRP modules with foam, concrete or soil for better insulation and energy absorption (such as for vehicle bumper beams and guard railings), or stability for soil retaining structures.
The fiber architecture of a FRP module comprises multiple layers of multi-axial stitched fabrics, unidirectional rovings, woven cloth, and mats, preferrably using glass or carbon fibers with a general purpose resin. The fiber architecture is continuous throughout the design of a FRP module such that a FRP module is a single, integral component and not comprised of separate pieces of fabric attached together. This fiber continuity through a FRP module provides adequate fiber reinforcement along main stress paths. In addition, a FRP module is manufactured using the conventional methods of the Seeman Composite Resin Infusion Molding Process (SCRIMP), Vacuum Assisted Resin Transfer Molding (VARTM), or pultrusion process.
The design of the FRP module of the present invention provides distinct advantages over the prior art. First, the shape of the FRP module lends itself to optimally place fabrics for maximum structural resistance. Second, the use of glass fiber reinforced thermoplastic rods with whiskers which melt during curing reinforce the intersections in the FRP module, ensure a better bond with other fabrics, and minimize voids where resin flow is most difficult. Third, the FRP module provides a lightweight, strong and durable structure that will not corrode like steel, spall like concrete, or rot like wood. The present design also provides a fiber and matrix architecture with inherent material properties that provide a high strength and stiffness to weight ratio, good fatigue resistance, and good corrosion resistance, thereby improving durability.
The panels and deck system made with the FRP modules of the present invention have a long service life and a reduced maintenance cost due to these fatigue and corrosion resistant properties, such that the life of a FRP module of the present invention can be approximately fifty years or better. This is accomplished by the fact that a deck made from FRP modules of the present invention is nearly ten times lighter than a traditional concrete bridge deck. Since the underlying support beams do not have to carry as much dead load, more live load can be applied giving the bridge a higher AASHTO rating.
The design of the FRP module also improves the performance of the structure over the prior art by addressing a common failurexe2x80x94web buckling. The instant design incorporates a diagonal web that connects a first and second vertical web, thereby reducing the unbraced length of the vertical webs. This in turn reduces the vertical webs"" buckling tendency. For example, the present FRP module design meets any of the general force transfer mechanisms, including AASHTO HS-25 truckload requirements.
The FRP modules of the present invention also have enhanced load bearing and interlocking capacity as compared with conventional FRP floor systems and building panels. The high load ratings are due to the high strength to weight ratio of the FRP modules, resulting in a panel or deck system employing the present FRP modules having higher load capacity than a reinforced concrete deck with much lower self weight. Further, stiffness of FRP modules in the direction perpendicular to traffic is adequate to provide the transverse load distribution to supporting beams.
The fiber architecture of the present invention is reinforced with heavy multi-axial stitched fabrics, continuous rovings, woven cloth and mats resulting in superior mechanical properties as compared to existing FRP composite lineal profiles. In addition, the composite fiber architecture overcomes the problems associated with moisture ingress and resin-dominated failure observed in panels with honeycomb core and outer skins.
FRP modules of the present invention can be properly designed, fabricated, and installed very efficiently. Such FRP modules can be used to replace deteriorated concrete or timber decks or to build new panel and deck systems. Further, such FRP modules can be assembled with composite stiffening beams to develop an all-composite short-span bridge superstructure.